The invention relates to an apparatus for the inductive transmission of electrical energy from a primary coil, which is arranged in a stationary unit, to a secondary coil, which is arranged in a vehicle.
Electrically driven vehicles require a charging apparatus in order to recharge the electrical energy storage device at regular intervals. Charging devices in which the user initiates the charging process by establishing contact between a charging cable and a socket which is fitted in the vehicle are not favorable on account of the lack of user-friendliness. Instead, the trend in electric vehicles is toward charging apparatuses which are based on contactless energy transmission.
In general, the at least one primary coil generates a magnetic field which allows energy transmission to the secondary coil across an air gap. However, efficient and reliable energy transmission over the air gap requires good positioning of the primary coil and the secondary coil, and the optimum position is therefore when the vehicle is parked above the apparatus such that the secondary coil is located exactly above the primary coil. However, if the vehicle is parked offset from the optimum position, the losses increase and, at the same time, the charging time increases.
EP 2 113 180 A2 discloses an apparatus for the inductive transmission of electrical energy, which apparatus is in the form of a carpet and comprises current conductors which are woven in as threads. An electrical load which is placed on the apparatus can be supplied with energy independently of the position of the load.
DE 10 2009 033 239 A1 proposes an apparatus for the inductive transmission of electrical energy in which a large number of identical primary coils which are arranged in the manner of a matrix is provided. In order to compensate for any offset which may occur between the stationary primary coil and the secondary coils which are arranged in the vehicle, provision is made to supply power in each case to those primary coils which are in line with corresponding secondary coils of a vehicle which is parked above the apparatus. However, the structural outlay for the large number of separate primary coils and secondary coils is high.